Hybrid indica rice(Oryza sativa L.) cultivars play an important role in rice production system due to its heterosis,resistance to environmental stress,large panicle,and high yield potential.However,no attention has been given to its root growth dynamic responses to rising atmospheric CO2 concentration([CO2 ]) in conjunction with nitrogen(N) availability.Free air CO2 enrichment(FACE) and N have significant effects on rice root growth.In this experiment,a hybrid cultivar Shanyou 63(Oryza sativa L.) was used to study the effects of FACE and N levels on roots growth of rice.The results showed a significant increase in both adventitious root volume(ARV) and adventitious root dry weight(ARD) under the FACE treatment.The application of nitrogen also increased ARV and ARD,but the increase was smaller than that under FACE treatment.On the basis of the FACE experiment,numerical models for rice adventitious root volume and dry weight were built with the time as the driving factor.The models illustrated the dynamic development of rice adventitious root volume and dry weight after transplanting,regulated either by the influence factor of atmospheric [CO2 ] or by N application.The models were successfully used to predict ARV and ARD under FACE treatment in a different year with the predicted data being closely related to the actual experimental data.The model had guiding significance to growth regulation of rice root under the condition of atmospheric [CO2 ] rising in the future. Hybrid indica rice (Oryza sativa L.) cultivars play an important role in rice production system due to its heterosis, resistance to environmental stress, large panicle, and high yield potential. However, no attention has been given to its root growth dynamic responses to rising atmospheric CO2 concentration ([CO2]) in conjunction with nitrogen (N) availability. Free air CO2 enrichment (FACE) and N have significant effects on rice root growth.In this experiment, a hybrid cultivar Shanyou 63 (Oryza sativa L.) was used to study the effects of FACE and N levels on roots growth of rice. The results showed a significant increase in both adventitious root volume (ARV) and adventitious root dry weight (ARD) under the FACE treatment. application of nitrogen also increased ARV and ARD, but the increase was smaller than that under FACE treatment. On the basis of the FACE experiment, Numerical models for rice adventitious root volume and dry weight were built with the time as the driving factor. The models illus trated the dynamic development of rice adventitious root volume and dry weight after transplanting, regulated either by the influence factor of atmospheric [CO2] or by N application. The models were successfully used to predict ARV and ARD under FACE treatment in a different year with the predicted data being closely related to the actual experimental data. the model had guiding significance to growth regulation of rice root under the condition of atmospheric [CO2] rising in the future.